Dab tsi yog kub dov me me steel vaj huam sib luag lub kaum ntse ntse thiab nws siv rau dab tsi? Qhov sib npaug ntawm lub kaum sab xis yog dav siv rau kev ua haujlwm dav dav, tsim cov ncej, kev siv tsheb, thiab hauv kev tsim kho kev lag luam. Lub kaum sab xis muaj 90 degree kaum sab xis nyob rau hauv nruab nrab ntawm qhov profile thiab ob sab muaj qhov dav sib npaug.
